(Reuters) — United Continental Holdings Inc. said on Thursday it was taking Boeing Co.'s grounded 787 Dreamliner out of its flying plans through June 5, except for a Denver-to-Tokyo route scheduled for a tentative launch in May.

Meanwhile, Japanese investigators studying fuel leaks on the 787 found a problem with the paint on equipment controlling the fuel-tank valve, the Nikkei news service reported, citing people familiar with the details.

United's decision to mostly exclude the 787 from its schedule until June comes as other airlines that have 787s are setting schedules for coming months while still uncertain about when the plane will be able to resume service.

The Dreamliner fleet has been grounded for the past five weeks after batteries burned on two planes in January. Boeing is due to meet with the head of the U.S. Federal Aviation Administration on Friday to present measures designed to prevent such failures, a source told Reuters, even though the root cause of the problem has not been determined.

United spokeswoman Christen David said in a statement on Thursday that the carrier's Denver to Tokyo Narita International route, originally set to start March 31, had been postponed to May 12. The launch would ultimately depend on a successful resolution of the safety incidents that have grounded the 787. Other service with the 787 won't resume until after June 5, David said.

"We are taking the 787 out of our schedule through June 5, except for Denver-Narita, which will tentatively launch on May 12," United's statement said.

Boeing was not immediately available for comment.

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United's statement doesn't mean that the 787 won't be ready to fly again before June 5, said Carter Leake, an analyst at BB&T Capital Markets.

Rather, it means United won't put the jet into service before then. If the plane is available sooner, but United can't use it on its scheduled routes, Boeing likely would have to pay United compensation that Mr. Leake estimates at about $800,000 a month, based on lease rates.

"This does not tell you that Boeing's plane is grounded until June," he said. "It tells you that Boeing's costs to United could be as if it's grounded until June."

A "superbox" to contain the battery or some other fix "might come sooner, but United is not paying" to have the jet until after June 5, he addded.

In a similar move, Poland's national airline LOT said last week that it would not use the 787 before October and that it is seeking compensation from Boeing.

United is the only U.S. carrier currently operating the 787 and has six of the planes, worth $207 million apiece at list prices. Japan Airlines and All Nippon Airways have most of the 50 jets delivered to airlines so far.

Meanwhile, Japan's Nikkei newspaper, citing sources, reported in its Feb. 22 morning edition that Transport Ministry investigators found deficiencies in how electrical-insulating paint was applied to a driving mechanism that opens and closes the 787's fuel-tank valve. The ministry also found foreign matter stuck on a switch on the mechanism.

The ministry is discussing the cause and measures to prevent recurrences with the U.S. FAA and Boeing, the Nikkei report added.

In addition to the battery problem, investigators have been looking into a case in which a Japan Airlines 787 leaked fuel while taxiing to the runway for take-off at Boston's Logan International Airport in January.